"Excuse me, there is a problem with our seat. I have 29C."
"What seems to be the issue, Sir?"
"It's becuase there's two of us"-pointing at wife. "And there's only one 29C seat."
"Then I can only assume your wife has the one next to it allocated to her."
"Let's have a look at the lady's boarding pass...29D it is."
"Oh, allright then."